# Regulation of re-replication in mammalian cells > **NIH NIH R01** · UNIVERSITY OF VIRGINIA · 2021 · $159,000 ## Abstract Project Summary Mammalian cells have evolved multiple non-overlapping mechanisms to ensure that DNA replication initiates from origins of replications once and only once in each division cycle; loss of control over these mechanisms induces genomic instability, an important driver of malignant transformation. Increasing evidence suggests that origin utilization and activation in higher eukaryotes is influenced by epigenetic factors, but exact mechanisms are largely undefined. Our long-term goals are to elucidate the underpinning mechanisms that control replication initiation in mammalian cells and to understand how perturbations of these mechanisms provokes genomic instability. The histone methyltransferase SET8 is emerging as a key regulator of replication initiation in mammalian cells through its mono-methyltransferase activity on histone H4K20. The cell cycle regulated enzyme is essential for origin licensing in G1 phase of the cell cycle, but is proteolytically degraded in S-phase; blocking this step triggers reiterative replication initiation within the same cell cycle or re-replication. Both SET8 and H4K20me, however, are also involved in transcriptional repression and in the repair of DNA double strand breaks (DSBs), but whether these seemingly independent activities play a role in replication initiation or re-replication is not known. Most importantly, little to nothing is known about the nature or characteristics of the re-replication products that accumulate in cells with defective SET8 degradation, nor is there information on where in the genome re-replication occurs or if there are certain genomic regions that are more prone to re-replication induction. Our new results show that re-replication resulting from defective SET8 degradation is not a stochastic process with few genomic sites exhibit large and significant copy number gains, reminiscent of genomic amplifications that are seen in cancer cells. Additional preliminary studies suggest that re-replication may originate from DNA double strand breaks (DSBs) that may spontaneously arise during replication, and requires the activity of genes involved both in transcriptional silencing and in DSB repair. Our innovative preliminary studies and experimental approaches are designed to thoroughly examine this alternative model of re-replication induction. Aim 1 we will determine the magnitude (copy number gains) and genomic distribution of the re- replicated DNA in cells with defective SET8 degradation and following the induction of DSBs. We will also test if these parameters vary in different cancer cell types and in cancer vs. non-cancer cells. Aim 2 will determine the chromatin occupancy of aberrantly stabilized SET8 and methylated H4K20 in cells with defective SET8 degradation, and whether these overlap with regions of re-replicated DNA. Aim 3 will define the role of transcriptional repression and DSB repair proteins in re-replication induction. The successful execution of the proposed ai... ## Key facts - **NIH application ID:** 10387262 - **Project number:** 3R01GM135376-02S1 - **Recipient organization:** UNIVERSITY OF VIRGINIA - **Principal Investigator:** TAREK A. ABBAS - **Activity code:** R01 (R01, R21, SBIR, etc.) - **Funding institute:** NIH - **Fiscal year:** 2021 - **Award amount:** $159,000 - **Award type:** 3 - **Project period:** 2020-03-01 → 2024-12-31 ## Primary source NIH RePORTER: https://reporter.nih.gov/project-details/10387262 ## Citation > US National Institutes of Health, RePORTER application 10387262, Regulation of re-replication in mammalian cells (3R01GM135376-02S1). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10387262. Licensed CC0. --- *[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*